The difference between the colon, the semicolon, and the em-dash

One of the quickest ways to make your writing look professional is to learn the difference between the colon, the semicolon, and the em-dash. There are many amateur writers that will go to great lengths to avoid using these pieces of punctuation out of a fear that they will inadvertently misuse them; however, learning to use them properly will add a variety and nuance to your writing that sends a signal to readers that you have mastered the basics of your craft.

While the rules themselves are relatively simple, even accomplished writers will find themselves retreating back to their style guides when questioned about the exact difference between these pieces of punctuation, so some confusion is understandable. The basic differences between the colon, the semicolon, and the em-dash can be summed up with three words: link, expand, and replace. The semicolon—the most feared of the lot—simply links two complete sentences together, the colon helps expand upon a single sentence, and the em-dash is used to replace other pieces of punctuation.

For an example of the proper use of a semicolon ( ; ), consider the following two sentences:

There is a monster under my bed. He has long teeth and sharp claws.

Each of these sentences are independent clauses, meaning they have both a subject (“There”, “He”) and a predicate (“is”, “has”). There is technically nothing wrong with keeping them apart, but the use of a period between the two sentences inserts a brief pause indicating that these are two separate thoughts. Linking the two sentences together with a semicolon reduces this pause:

There is a monster under my bed; he has long teeth and sharp claws.

The result is writing that sounds more natural and less like a monologue from William Shatner.

A semicolon can also be used in conjunction with the words “however” and “for example” to further elaborate on an idea; however, this tends to be used more in academic writing and often lends an unnatural or pretentious tone to your writing, so it should be used sparingly.

Finally, a semicolon can be used to clarify lists using multiple commas. Consider this confusing sentence:

The intent of this sentence is to indicate the speaker’s relationship with three victims, but the confusing use of commas make it seem as if there are four victims: Tommy, Billy, an unnamed boy, and Sally. This can be clarified with the use of semicolons:

The colon ( : ) has a comparatively simple function than the semicolon—it is used to introduce a word or phrase that expands upon a sentence. Consider the following example:

The monster likes to eat a particular organ: eyes.

The sentence “The monster likes to eat a particular organ” makes sense on its own, but, unlike with the semicolon, “eyes” does not. It is a single detail being connected to a thought in a way that expands it and adds a bit of a dramatic punch.

Colons can also be used to expand a sentence by introducing a list:

The monster eats the following organs: eyes, spleens, gallbladders, and livers.

Or by introducing a quote:

My grandpa always said: “You can’t kill a monster. You only drive it away for a little while.”

The final important piece of punctuation to learn about is the em-dash ( — ). The use of the em-dash is a matter of style. It is used to replace other pieces of punctuation, particularly commas and parentheses, and generally indicates an interruption in the normal flow of a sentence. For example:

The monster, a hairy beast with sharp teeth, dragged my father under my bed.

There’s nothing wrong with this sentence and some people might prefer the use of commas. However, another option is to replace the commas with em-dashes:

The monster— a hairy beast with sharp teeth— dragged my father under my bed.

This gives a writer the option of adding a little variety to their punctuation. It can also be used to visually emphasize elements a writer wants to call attention towards.

Em-dashes can also be used to replace colons:

There was only one person left for the monster to eat— me.

However, writers should be careful not to overuse the em-dash. It is a very useful tool, but generally if it is used more than twice in a single paragraph it becomes distracting and a little confusing. Writers should also be careful not to mistake the em-dash for a hyphen ( – ) or an en-dash ( – ).

All three of these pieces of punctuation’s should be available in any writer’s toolbox. Their deliberate exclusion from a piece of writing is a strong indicator to readers of the writer’s lack of experience or confidence. Don’t be afraid of them and don’t avoid them, because learning their proper use is an excellent step towards being able to write in a way well-suited to anything from the next great novel to the next great office memo.

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